Method of hot forming nickel steel by pressure dies



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March 13, 1962 J. A. GuLYA 3,024,529

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METHOD OF HOT FORMING NICKEL STEEL BY PRESSURE DIES Filed May l, 1958 4 Sheets-$heet 4 Ivecm'ng cycle I I coolngcycle |900 pressing |500 finishing temperature fnshlng emperafw'e IL Crbc-m SteeI l Temperature, n F.

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John Gu/ya.

ifo/"Hey,

United States PatentCtitice 3,024,529 Patented Mar. 13, 1962 3,024,529 METHOD F HOT FORMING NICKEL STEEL BY PRESSURE DIES John Anthony Gulya, Lancaster, Pa., assignor to Lukens Steel Company, Coatesville, Pa., a corporation of Penn- Sylvania Filed May 1, 1958, Ser. No. 732,216 4 Claims. (Cl. 29-552.3)

The present invention is directed to a method of pressing 9% nickel steel heads. For the purpose of this invention a head is a steel shape such as a half sphere or a variation of the same which is adapted to be hot formed to shape by pressure dies.

It is the usual practice in steel plants or other metal working plants Where dies are used in the hot forming of heads to provide dies of a deiinite size for pressing heads from carbon steels. Dies are so designed that the thermal contraction of carbon steel from about 1l00 F. to room temperature permits the desired size of the steel article to be obtained. The differences in contraction through this range for carbon, as Well as somey alloy steels, is insufficient to cause final sizes outside of the usual tolerances.

Carbon steel plates are normally heated for pressing, utilizing certain size dies in accordance with the steel composition, gauge, and intended shape. In other words, these factors determine the size of the dies that are used in the hot forming or shaping operation. The minimum temperature required is such that most of the deformation occurs While the steel is in a plastic state. Temperatures exceeding this requirement waste furnace time and reduce production. Insufficient temperature will permit excessive deformation in the elastic state and the head will be too large as a result of spring-back. Consequently, a heating temperature is selected to provide a finishing temperature on the order of about 1100 F. for 1/2" carbon steel. As noted above, the differences in contraction and springback in carbon steel and some alloy steels is such as to be within normal tolerances.

lt can be determined that from a iinishing temperature 1 of 1l00 F. to room temperature, carbon steel will contract about .009 in./in. Over the same range, 9% nickel steel contracts about .003 in./in. The difference in contraction, amounting to about .006` in./in., is suiiicient to cause 9% nickel steel heads pressed on dies for carbon steel to exceed the usual oversize tolerances.

Consequently, it would appear to be necessary to provide additional dies for forming heads from 9% nickel steel. The production of pressed heads from 9% nickel steel may constitute only a small percentage of the heads produced by the steel plant which is ordinarily engaged in the production of carbon steel heads, thus making it necessary to provide such additional dies for the 9% nickel steel head production, plus the additional expense of storage and maintenance of the different size dies that are used in the production of 9% nickel steel heads.

By means of the method of the present invention, it will be possible to use the same set of dies for the production of carbon steel heads, as well as for 9% nickel steel heads. This result is attainable by varying the heating method in accordance with the type of steel which is hot formed to shape pressing dies, and as a result it is possible to use one set of dies for hot forming both carbon steel heads and nickel steel heads, and to produce pressed heads whose final sizes are within the usual tolerances.

ln the drawings:

FIGURE 1 is a diagrammatic showing, by way of illustration, of a set of forming dies and their mounting;

FIGURE 2 is a graph showing the effect of finishing temperature using the same dies and temperature as it affects the size of heads of 9% nickel steel;

FIGURE 4 is a graph showing the effect of finishing temperature in accordance with the teaching of this invention, but using the same dies as used in the production of the graphs of FIGURES 2 and 3, as it affects the size of heads of 9% nickel steel;

FIGURE 5 is a schematic diagram illustrating the pressing and thermal cycles using dies for carbon steel and pressing a carbon steel head;

FIGURE 6 is a schematic diagram illustrating the same pressing and thermal cycles and the same dies in the pressing of 9% nickel steel;

FIGURE 7 is a schematic diagram illustrating the same pressing cycle and the same dies but a different heat cycle than that illustrated in FIGURES 4 and 5 for pressing 9% nickel steel.

The chemical analysis of 9% nickel steel is as follows:

Balance iron with residuals Cu, Mo, Cr, P, S, etc. but preferred carbon range is .02% to .12%.

As shown diagrammatically in FIGURE l, which is shown for illustrative purposes only, a fluid press A is provided with a stationary die member 10 and a removable die member 12 for making curved heads. The die members, it will be understood, may be of any desired shape for hot pressing a finished head to the desired configuration or form. It will further be understood that the dies are designed or constructed for pressing carbon steel plates or other shapes to their intended final shapes.

The graph shown in FIGURE 2 illustrates the heating cycle and shows the expansivity of carbon steel. In order to provide a minimum temperature, such that the greater part of deformation occurs while the steel is in a plastic state, whereby to prevent wastage of furnace time and reduced production While nevertheless providing sufiicient heat to prevent excessive deformation in the elastic state, a heating temperature is selected which will provide a finishing temperature on the order of about 1100 F. for 1/2 carbon steel. The design of the dies is such that the thermal contraction of the pressed carbon steel head from 1100 F. to room temperature results in the desired pressed head size. This is due to the fact that the difference in contraction throughout this range for carbon and some alloy steels is insuicient to cause nal sizes which are greater than the usual tolerances.

I have discovered that it is possible to use standard carbon steel dies for pressing 9% nickel steel shapes within the usual tolerances, by increasing the finishing temperature. This is accomplished either by directly increasing heating temperatures or by reheating before the completion of the pressing operation. For instance, when hot pressing 1/2 nickel steel plates an initial heating temperature on the order of 1950 F. would be required for such steel, instead of the usual temperature of 1650o F.

By reference to FIGURE 4, it will be noted that the additional .006 in./in. shrinkage would require a sizing temperature of about 1650 F. However, this temperature is in the plastic range for steels and little spring-back would be encountered. Therefore, a minimum temperature on the order of 1500 F. should be tolerable. A further reduction in finishing temperature, say to 1400 F. is possible if the head is purposely oversize, but without tolerance.

FIGURE 4 illustrates in dash line for carbon steel and in full line for 9% nickel steel typical thermal cycles of the types further illustrated in FIGURES 2 and 3, respectively. The pressing range for both cycles is illustrated by the curved full and dash lines between the vertical dash lines centrally located in FIGURE 4.

The diagram shown in FIGURE 5 shows that when using dies designed for carbon steel for pressing carbon steel heads with a iinishing temperature of about 1100 F., the combined spring-hack (elastic deformation) C, and thermal contraction B provides a carbon steel head of the desired size.

The diagram shown in FIGURE 6 shows the use of the same dies under the same heat conditions (as FiGURE 5). When using 9% nickel steel heads, the eliects of spring-back D, thermal contraction E, and phase change F, results in oversize heads as seen at G.

The diagram shown in FIGURE 7 shows the use of same dies, i.e., as heretofore described with reference to FIGURES 5 and 6, the same being the dies used in the pressing of carbon steel heads of the shape and size for use in pressing of 9% nickel steel heads. However, as shown in the diagram, the finishing temperature has been increased to about 1500 F. whereby to provide the balance in spring-back H, thermal contraction I, and phase change expansion I sufficient to produce a 9% nickel steel head within the same tolerances as those of carbon steel heads produced with the same dies.

The term 9% nickel steel or similar terminology in the specification and claims is intended to mean steel wherein the nickel content is between 8.5% to 9.5%, as disclosed above following the description of FIGURE 7.

The above description and drawings disclose a single embodiment of the invention, and specific language has been employed in describing the ligures. It will, nevertheless, be understood that no limitations of the scope of the invention are thereby contemplated, and that various alterations and modifications may be made as would occur to one skilled in the art to which the invention relates.

I claim:

1. ln the method for hot die pressing a nickel steel plate into head shape in which said plate is initially heated to the plastic state, pressed and cooled to room temperature, the improvement comprising providing standard carbon steel dies used for pressing curved carbon steel heads and providing a finishing temperature of at least about 1500 F. before completing the pressing of a nickel steel plate having the same dimensions as carbon steel heads which are made of carbon steel plate and used in said dies, said nickel steel plate having a composition range of C-.12% maximum, Ni-8.59.5%, Mn-.35-.80%, Si-.15-.30%, the balance iron with residuals, in order to increase shrinkage and provide substantially the same tolerances in the finished nickel steel head as would be provided in a carbon steel head utilizing the same dies at a temperature range of at least 300 F. less than the temperature at which the nickel steel plate is treated, and reheating to a temperature of at least 1500 F.

2. The method ot claim 1 wherein the nickel steel plate is initially heated to a temperature of about 1950 F. before being pressed.

3. In the method for hot die pressing a nickel steel plate into head shape in which said plate is initially heated to the plastic state, pressed and cooled to room temperature, the improvement comprising providing standard carbon steel dies used for pressing curved carbon steel heads and providing a finishing temperature of at least about 1500 F. before completing the pressing of a nickel steel plate having the same dimensions as carbon steel heads which are made of carbon steel plate and used in said dies, said nickel steel plate having a composition range of C--.09%, Ni-9.0%, Mn-.60%, Si-.22%, the balance iron with residuals, in order to increase shrinkage and provide substantially the same tolerances in the finished nickel steel head as would be provided in a carbon steel head utilizing the same dies at a temperature range of at least 300 F. less than the temperature at which the nickel steel plate is treated, and reheating to a temperature of at least 1500 F.

4. The method of claim 3 wherein the nickel steel plate is initially heated to a temperature of about 1950 F. before being pressed.

References Cited in the tile of this patent UNITED STATES PATENTS 397,179 Fox Feb. 5, 1889 2,040,957 Sanders May 19, 1936 2,451,469 Brophy et al. Oct. 19, 1948 OTHER REFERENCES Nickel in Iron and Steel, by A. M. Hall, 1954, pub. for The Engineering Foundation `by John Wiley & Sons, Inc., New York, pp. 2 and 31 relied on. 

1. IN THE METHOD FOR HOT DIE PRESSING A NICKEL STEEL PLATE INTO HEAD SHAPE IN WHICH SAIDF PLATE IS INITIALLY HEATED TO THE PLASTIC STATE, PRESSED AND COOLED TO ROOM TEMPERATURE, THE IMPROVEMENT COMPRISING PROVIDING STANDARD CARBONSTEEL DIES USED FOR PRESSING CURVED CARBON STEEL HEADS AND PROVIDING A FINISHING TEMPERATURE OF AT LEAST ABOUT 1500* F. BEFORE COMPLETING THE PRESSING OF A NICKEL STEEL PLATE HAVING THE SAME DIMENSION AS CARBON STEEL HEADS WHICH ARE MADE OF CARBON STEEL AND 